Oil pump

ABSTRACT

An oil pump includes a first control valve including a first valve body provided in a first valve housing for reciprocating therein, the first valve body for controlling discharge pressure of working oil discharged from a pump main body, a first valve chamber formed in the first valve housing, the first valve chamber being applied with the discharge pressure of the working oil from the pump main body, and a second valve chamber formed in the first valve housing, the second valve chamber being supplied with the working oil, and a second control valve activated on the basis of degree of the temperature of the working oil, the second control valve for controlling oil pressure of the working oil flowed into the second valve chamber.

This application is based on and claims priority under 35 U.S.C. § 119to Japanese Patent Application 2005-025198, filed on Feb. 1, 2005, theentire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to an oil pump with control valves forcontrolling a discharge pressure of working oil.

BACKGROUND

A known oil pump for controlling a discharge pressure of working oil isdisclosed in JP3531769B. As illustrated in FIG. 15, the disclosed oilpump includes a pump main body 101 having a pump chamber 110, a rotor102 rotating in the pump chamber 110 by means of a drive source, aninlet port 136 sucking the working oil into the pump chamber 110 inresponse to a rotation of the rotor 102, first and second outlet ports131 and 132 discharging the working oil out of the pump chamber 110 inresponse to the rotation of the rotor 102, a first oil passage 151, asecond oil passage 152, a feedback oil passage 106, a control unit 107,and a control valve 104. The first oil passage 151 connects a dischargeoil passage 105, which is communicated with parts to be supplied withthe working oil, to the first outlet port 131, and delivers the workingoil to the discharge oil passage 105 discharged from the first outletport 131. The second oil passage 152 connects the discharge oil passage105 to the second outlet port 132, and delivers the working oil to thedischarge oil passage 105 from the second outlet port 132. The feedbackoil passage 106 is connected to the second oil passage 152 andcommunicated with the inlet port 136. The control unit 107 outputs acontrol signal on the basis of degree of oil pressure of the first oilpassage 151, degree of oil temperature, degree of throttle angle, degreeof rotational speed of an internal combustion engine serving as thedrive source, or the like. The control valve 104 is connected to thefirst oil passage 151, the second oil passage 152, and the feedback oilpassage 106, and activated on the basis of the control signal of thecontrol unit 107.

On this occasion, the control valve 104 is activated by means of aproportional electromagnetic control mechanism 108. The control unit 107directly or indirectly detects the oil pressure of the first oil passage151, the oil temperature, the throttle angle, and the rotational speedof the internal combustion engine. Further, the control unit 107 outputsthe control signal for operating the control valve 104, on the basis ofthe signal detected, for obtaining a predetermined dischargecharacteristic. Thereby, on the basis of use conditions of the internalcombustion engine, the disclosed oil pump offers an optimal dischargepressure by means of an electromagnetic control, and reduces anoperation of the pump more than required.

However, the disclosed oil pump includes the proportionalelectromagnetic control mechanism 108 such as a solenoid, or the like,for activating the control valve 104, the control unit 107 forgenerating the control signal relative to the proportionalelectromagnetic control mechanism 108, and a detecting mechanism such asa sensor, or the like, for outputting information such as degree of theoil pressure, degree of the oil temperature, degree of the throttleangle, or the like, relative to the control unit 107. With theconfiguration of such oil pump, a structure for controlling thedischarge pressure of the oil pump may be complicated and amanufacturing cost of the oil pump may occasionally be expensive.

A need thus exists for an oil pump, which appropriately controls thedischarge pressure on the basis of a temperature of the working oil witha simple structure.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an oil pump includes afirst control valve including a first valve body provided in a firstvalve housing for reciprocating therein, the first valve body forcontrolling discharge pressure of working oil discharged from a pumpmain body, a first valve chamber formed in the first valve housing, thefirst valve chamber being applied with the discharge pressure of theworking oil from the pump main body, and a second valve chamber formedin the first valve housing, the second valve chamber being supplied withthe working oil, and a second control valve activated on the basis ofdegree of the temperature of the working oil, the second control valvefor controlling oil pressure of the working oil flowed into the secondvalve chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the presentinvention will become more apparent from the following detaileddescription considered with reference to the accompanying drawings,wherein:

FIG. 1 is a conceptual view illustrating a structure of an oil pumpaccording to a first embodiment of the present invention.

FIG. 2 is a view illustrating a flow of working oil of a state A withoutshowing a main body of the oil pump according to the first embodiment ofthe present invention.

FIG. 3 is a view illustrating a flow of the working oil of a state Bwithout showing the main body of the oil pump according to the firstembodiment of the present invention.

FIG. 4 is a view illustrating a flow of the working oil of a state Cwithout showing the main body of the oil pump according to the firstembodiment of the present invention.

FIG. 5 is a view illustrating a flow of the working oil of a state Dwithout showing the main body of the oil pump according to the firstembodiment of the present invention.

FIG. 6 is a view illustrating a flow of the working oil of a state Ewithout showing the main body of the oil pump according to the firstembodiment of the present invention.

FIG. 7 is a view illustrating a flow of the working oil of anintermediate state without showing the main body of the oil pumpaccording to the first embodiment of the present invention.

FIG. 8 is a view illustrating a flow of the working oil of a hightemperature state without showing the main body of the oil pumpaccording to the first embodiment of the present invention.

FIG. 9A is a graph indicating a relation, within a normal temperatureregion of the working oil, between a rotational speed of a rotor and adischarge pressure of the working oil at a discharge oil passage of theoil pump according to the first embodiment of the present invention.

FIG. 9B is a graph indicating a relation, within a high temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof the oil pump according to the first embodiment of the presentinvention.

FIG. 10A is a graph indicating a relation, within the normal temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof an oil pump, which includes a first control valve similar to that ofthe first embodiment of the present invention, and does not include asecond control valve.

FIG. 10B is a graph indicating a relation, within the high temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof the oil pump, which includes the first control valve similar to thatof the first embodiment of the present invention, and does not includethe second control valve.

FIG. 11 is a conceptual view illustrating a structure of an oil pumpaccording to a second embodiment of the present invention.

FIG. 12A is a graph indicating a relation, within the normal temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof the oil pump according to the second embodiment of the presentinvention.

FIG. 12B is a graph indicating a relation, within the high temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof the oil pump according to the second embodiment of the presentinvention.

FIG. 13A is a graph indicating a relation, within the normal temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof an oil pump, which includes the first control valve similar to thatof the second embodiment of the present invention, and does not includethe second control valve.

FIG. 13B is a graph indicating a relation, within the high temperatureregion of the working oil, between the rotational speed of the rotor andthe discharge pressure of the working oil in the discharge oil passageof the oil pump, which includes the first control valve similar to thatof the second embodiment of the present invention, and does not includethe second control valve.

FIG. 14 is a conceptual view illustrating a structure of an oil pumpaccording to a third embodiment of the present invention.

FIG. 15 is a conceptual view illustrating a structure of an oil pump ofa known art.

DETAILED DESCRIPTION

Embodiments of the present invention will be explained hereinbelow withreference to the attached drawings. According to the embodiments of thepresent invention, an oil pump X is explained as an example, which isapplied to a vehicle and supplies working oil to each part of an engineby generating an oil pressure by means of the engine serving as a drivesource.

As illustrated in FIG. 1, the oil pump X according to the firstembodiment of the present invention includes a pump main body 1 having arotor 2 rotated by means of a crankshaft, first and second outlet ports31 and 32 discharging the working oil out of the pump main body 1, aninlet port 36 sucking the working oil into the pump main body 1, adischarge oil passage 5 communicating with each part of the engine, orthe like, to be supplied with the working oil, a first control valve 4controlling a discharge pressure of the working oil from the pump mainbody 1, a second control valve 7 activated on the basis of degree oftemperature of the working oil and controlling an operation of the firstcontrol valve 4, and a feedback oil passage 6 feeding back surplusworking oil passed through the first control valve 4 to the inlet port36 side. Each component will be explained in detail hereinbelow.

The pump main body 1 of the oil pump X is made of metal (e.g.aluminum-based alloy, an iron-based alloy, or the like) and formed witha pump chamber 10 inside thereof. The pump chamber 10 is formed with aninternal gear portion 12. The internal gear portion 12 is provided witha plurality of internal gear teeth 11 so as to constitute a driven gear.

The metal rotor 2 is rotatably provided at the pump chamber 10. Therotor 2 is connected to the crankshaft of the engine serving as thedrive source, and is synchronously rotatable with the crankshaft. Forexample, the rotor 2 is designed to rotate at a revolving speed of from600 to 7,000 rpm. The rotor 2 is formed with an outer gear portion 22.The outer gear portion 22 is provided with a plurality of outer gearteeth 21 so as to constitute a drive gear. The internal gear teeth 11and the outer gear teeth 21 are defined by a trochoid curve, a cycloidcurve, or the like. The rotor 2 rotates in a direction of arrow A1 shownin FIG. 1. In accordance with a rotation of the rotor 2, the outer gearteeth 21 of the rotor 2 are meshed with the internal gear teeth 11 oneafter another, and accordingly the internal gear portion 12 is rotatedin the identical direction to the rotor 2. Between the outer gear teeth21 and the internal gear teeth 11, there are formed spaces 22 a-22 k. InFIG. 1, a space 22 f has the largest volume, and the spaces 22 a and 22k have the smallest volume. On this occasion, for example, because thevolume of the spaces 22 a-22 e is enlarged, the spaces 22 a-22 e producean inlet pressure and they act to suck the working oil. In contrast,because the volume of the spaces 22 g-22 k is diminished, the spaces 22g-22 k produce the discharge pressure and they act to discharge theworking oil.

The pump main body 1 is provided with, at a first side thereof, anoutlet port array 33 having the first and second outlet ports 31 and 32discharging the working oil out of the pump main body 1. The outlet portarray 33 discharges the working oil out of the pump chamber 10 inaccordance with the rotation of the rotor 2. The first outlet port 31 isprovided with end side portions 31 a and 31 c, and the second outletport 32 is provided with end side portions 32 a and 32 c. The first andsecond outlet ports 31 and 32 are communicated with the discharge oilpassage 5. Further the pump main body 1 is provided with, at a secondside thereof, the inlet port 36. The inlet port 36 sucks the working oilinto the pump chamber 10 in accordance with the rotation of the rotor 2.The inlet port 36 is provided with end side portions 36 a and 36 c. Theinlet port 36 is communicated with an inlet oil passage 8 communicatingwith an oil pan, or the like.

According to the embodiment of the present invention, the first outletport 31 is disposed upstream relative to the second outlet port 32 in arotational direction of the rotor 2 indicated by the arrow A1 in FIG. 1.An opening area of the first outlet port 31 is configured so as to belarger than that of the second outlet port 32.

The first and second outlet ports 31 and 32 are separated by means of aseparating member 37. Thus, each of the first and second outlet ports 31and 32 has an individual discharge function. For example, a width of theseparating member 37 may be configured to be narrower than a teethmargin positioned between the first outlet port 31 and the second outletport 32 in order to prevent an increase of the oil pressure, which iscaused by a confinement of the working oil at the teeth margin during acompressing process of a space of the teeth margin between the internalgear teeth 11 and the outer gear teeth 21 by means of the rotation ofthe rotor 2.

The discharge oil passage 5 communicates with each part of the engine,or the like, to be supplied with the working oil, and supplies theworking oil thereto. More particularly, the discharge oil passage 5supplies the working oil to each part of the engine, which requires alubrication by means of the working oil or an activation by means of theoil pressure, for example, a bearing such as a journal of the crankshaftof the engine, a valve timing control apparatus, a sliding portionbetween a cylinder and a piston, or the like. Alternatively, or inaddition, the discharge oil passage 5 may be configured to supply theworking oil to various parts of the vehicle other than the engine.

According to the embodiment of the present invention, the discharge oilpassage 5 includes a port connecting oil passage 51, which communicatesthe first outlet port 31 with the second outlet port 32 through thefirst control valve 4. Further the first outlet port 31 directlycommunicates with the discharge oil passage 5, and the second outletport 32 communicates with the discharge oil passage 5 through the portconnecting oil passage 51 and the first outlet port 31. The firstcontrol valve 4 is provided in midstream of the port connecting oilpassage 51.

The feedback oil passage 6 feeds back the surplus working oil passedthrough the first control valve 4 to the inlet port 36 side.Alternatively, or in addition, the feedback oil passage 6 may becommunicated with the oil pan, or the like, to form a drain oil passage.

The first control valve 4 is provided in a first valve housing 41 forreciprocating therein. The first control valve 4 includes a first valvebody 42, a first valve chamber 43, a second valve chamber 44, and abiasing mechanism 45. The first valve body 42 controls the dischargepressure of the working oil discharged from the pump main body 1 on thebasis of its position in the first valve housing 41. As illustrated inFIG. 1, the first valve chamber 43 is formed below the first valve body42 in the first valve housing 41 and is applied with the dischargepressure of the working oil from the pump main body 1. As illustrated inFIG. 1, the second valve chamber 44 is formed above the first valve body42 in the first valve housing 41 and is capable of sucking the workingoil. The biasing mechanism 45 biases the first valve body 42 in adirection in which the first valve body 42 is moved toward the firstvalve chamber 43.

According to the embodiment of the present invention, the first controlvalve 4 establishes or interrupts a communication path between thesecond outlet port 32 and the discharge oil passage 5 by activating thefirst valve body 42 to establish or interrupt a communication path ofthe port connecting oil passage 51. Then, the first control valve 4performs a control for changing the discharge pressure of the operationoil to be discharged to the discharge oil passage 5 between thedischarge pressure only from the first outlet port 31 and the dischargepressure from both of the first and second outlet ports 31 and 32.Accordingly, the first control valve 4 controls the discharge pressureof the working oil from the pump main body 1.

The first valve body 42 is slidably provided in the substantiallycylindrical shaped first valve housing 41. According to the embodimentof the present invention, the first valve chamber 43 is located belowthe first valve body 42 as shown in FIG. 1, and the second valve chamber44 is located above the first valve body 42 as shown in FIG. 1. Thefirst valve chamber 43 communicates with the discharge oil passage 5through a first transmission oil passage 52. Thereby, the dischargepressure of the working oil applies to a first surface of the firstvalve body 42 (i.e., a lower surface of the first valve body 42 in FIG.1). In contrast, the second valve chamber 44 is provided with a spring45 a of the biasing mechanism 45. The first valve body 42 is biased in adirection in which the first valve body 42 is moved toward the firstvalve chamber 43 (a direction of B1 in FIG. 1) by means of the spring 45a. With the configuration of the oil pump according to the embodiment ofthe present invention, a position of the first valve body 42 is definedby means of a balance between a biasing force of the spring 45 a in thedirection in which the first valve body 42 is moved toward the firstvalve chamber 43 (the direction of B1 in FIG. 1) and a force of thedischarge pressure of the working oil in the first valve chamber 43 in adirection in which the first valve body 42 is moved toward the secondvalve chamber 44. Further, the second valve chamber 44 communicates withthe second control valve 7 through a first intermediate oil passage 91and a second intermediate oil passage 92. Therefore, the working oil canbe flowed into the second control chamber 44 through the second controlvalve 7.

The first valve body 42 is provided with two oil passages forcontrolling a destination of the working oil from the second outlet port32. According to the embodiment of the present invention, a first oilpassage 42 a is located at a second valve chamber 44 side (an upper sideas viewed in FIG. 1) and a second oil passage 42 b is located at a firstvalve chamber 43 side (a lower side as viewed in FIG. 1).

The first valve housing 41 includes first and second switch ports 41 aand 41 b, first and second feedback ports 41 c and 41 d, a dischargepressure port 41 e, and first and second back pressure ports 41 f and 41g. The first switch port 41 a communicates with the port connecting oilpassage 51 at a second outlet port 32 side, and the second switch port41 b communicates with the port connecting oil passage 51 at a firstoutlet port 31 side. The first and second feedback ports 41 c and 41 dcommunicate with the feedback oil passage 6. The discharge pressure port41 e applies the discharge pressure of the working oil to the firstvalve chamber 43 by communicating the first valve chamber 43 and thefirst transmission oil passage 52. The first back pressure port 41 fcommunicates with the first intermediate oil passage 91, and the secondback pressure port 41 g communicates with the second intermediate oilpassage 92.

The second control valve 7 controls the first control valve 4 on thebasis of degree of the temperature of the working oil. Moreparticularly, the second control valve 7 controls the oil pressure ofthe working oil flowed into the second valve chamber 44 of the firstcontrol valve 4 on the basis of degree of the temperature of the workingoil. According to the embodiment of the present invention, in acondition where the temperature of the working oil satisfies apredetermined temperature condition J, the second control valve 7performs a control for establishing a communication path between thesecond valve chamber 44 and the first valve chamber 43 by establishing acommunication path between the second valve chamber 44 of the firstcontrol valve 4 and the discharge oil passage 5. More particularly, in acondition where the temperature of the working oil satisfies thetemperature condition J, the second control valve 7 performs a controlfor moving the first valve body 42 of the first control valve 4 to alast end portion of the first valve housing 41 at the first valvechamber 43 side on the basis of a view that the oil pressure in thesecond valve chamber 44 is substantially equal to that of the firstvalve chamber 43. In contrast, in a condition where the temperature ofthe working oil does not satisfy the temperature condition J, the secondcontrol valve 7 performs a control for establishing a communication pathbetween the second valve chamber 44 of the first control valve 4 and thefeedback oil passage 6. On this condition, the oil pressure in thesecond valve chamber 44 is adequately lower degree than that of thefirst valve chamber 43. Therefore, the position of the first valve body42 is defined by means of the balance between the biasing force of thespring 45 a of the biasing mechanism 45 and the force of the oilpressure in the first valve chamber 43. Accordingly, the first controlvalve 4 controls the discharge pressure of the working oil to bedischarged to the discharge oil passage 5 by means of a movement of thefirst valve body 42 on the basis of degree of the discharge pressure ofthe working oil.

According to the embodiment of the present invention, the oil pump Xsupplies the working oil relative to each part of the engine of thevehicle. Thus, a temperature of the working oil under normal useconditions is assumed to be from room temperature to 110 degrees C., anda temperature of the working oil in a condition where the engine isactivated for long periods of time with a heavy load is assumed to behigher degree, for example, approximately from 110 to 130 degrees C.According to the embodiment of the present invention, in order to changean operating control of the first control valve 4 under such a hightemperature state, the temperature condition J is assumed to beapproximately from 110 to 130 degrees C.

According to the embodiment of the present invention, in order toperform the above described control, the second control valve 7 includesa second valve body 72 and a valve body operating mechanism 73. Thesecond valve body 72 reciprocates in a second valve housing 71 andchanges a control whether to establish or interrupt the communicationpath between the second valve chamber 44 and the first valve chamber 43.The valve body operating mechanism 73 activates the second valve body 72by means of a heat-sensitive expanding and contracting member 73 a,which is expanded and contracted in a direction of a reciprocation ofthe second valve body 72 on the basis of degree of the temperature ofthe working oil.

The second valve body 72 is slidably provided in the substantiallycylindrical shaped second valve housing 71. The second valve body 72 isprovided with a third oil passage 72 a for controlling a communicationpath of the second valve chamber 44 of the first control valve 4

The second valve housing 71 is provided with a high pressure port 71 a,a low pressure port 71 b, a drain port 71 c, a first communicating port71 d, a second communicating port 71 e, and a communicating passage 71f. The high pressure port 71 a communicates with the discharge oilpassage 5 through a second transmission oil passage 53 and the lowpressure port 71 b communicates with the feedback oil passage 6. Thedrain port 71 c communicates with the oil pan, or the like, the firstcommunicating port 71 d communicates with the first intermediate oilpassage 91, and the second communicating port 71 e communicates with thesecond intermediate oil passage 92. The communicating passage 71 fcommunicates the low pressure port 71 b with the third oil passage 72 aof the second valve body 72 in a condition where the second valve body72 positions within a predetermined range.

The valve body operating mechanism 73 is provided with, at a first sideof the second valve body 72 (an upper side as viewed in FIG. 1), theheat-sensitive expanding and contracting member 73 a, which is expandedand contracted in the direction of the reciprocation of the second valvebody 72 on the basis of degree of the temperature of the working oil.The valve body operating mechanism 73 is provided with, at a second sideof the second valve body 72 (a lower side as viewed in FIG. 1), anelastic member 73 b. According to the embodiment of the presentinvention, the elastic member 73 b includes a spring, and theheat-sensitive expanding and contracting member 73 a includes a springmade of shape memory alloy. The working oil from the feedback oilpassage 6 flows into a space in the second valve housing 71 in which theheat-sensitive expanding and contracting member 73 a is provided throughthe low pressure port 71 b. Therefore, the heat-sensitive expanding andcontracting member 73 a is normally soaked in the working oil and thetemperature of the working oil can be transmitted thereto. In acondition where the temperature of the working oil in the vicinity ofthe heat-sensitive expanding and contracting member 73 a satisfies thetemperature condition J, the heat-sensitive expanding and contractingmember 73 a expands in the direction of the reciprocation of the secondvalve body 72 and compresses the elastic member 73 b to move the secondvalve body 72 in a second side (the lower side as viewed in FIG. 1).According to the embodiment of the present invention, the temperaturecondition J is assumed to be approximately from 110 to 130 degrees C.Therefore, in a condition where the temperature of the working oil inthe vicinity of the heat-sensitive expanding and contracting member 73 abecomes equal to, or higher than, 110 degrees C., the heat-sensitiveexpanding and contracting member 73 a expands in the direction of thereciprocation of the second valve body 72 and moves the second valvebody 72 in a vertical direction.

The second control valve 7 is configured to activate independently fromthe first control valve 4. With the configuration of the pump main body1 of the oil pump X according to the embodiment of the presentinvention, the discharge pressure of the working oil is pulsated.However, the heat-sensitive expanding and contracting member 73 a is notinfluenced by a pulsation of the discharge pressure of the working oilbecause the second valve body 72 of the second control valve 7 isapplied with the discharge pressure of the working oil from a side facethereof through the high pressure port 71 a. Accordingly, even when theheat-sensitive expanding and contracting member 73 a includes a springmade of shape memory alloy, fatigue strength of which is at a lowerdegree, a fatigue breakdown of the spring is not generated.

An operation of the first control valve 4 and the second control valve 7in response to an increase of a rotational speed of the rotor 2 of thepump main body 1 and an increase of the temperature of the working oilwill be explained hereinafter. Illustrated in FIGS. 2-8 are a flow ofthe working oil in various conditions of the first control valve 4 andthe second control valve 7.

Further, illustrated in FIGS. 9A-9B are a relation, within a normaltemperature region of the working oil (approximately from roomtemperature to 110 degrees C.) and within a high temperature region ofthe working oil (approximately from 110 to 130 degrees C.), between therotational speed of the rotor 2 and the discharge pressure of theworking oil in the discharge oil passage 5. FIG. 9A indicates acondition where the temperature of the oil is approximately 80 degreesC. and FIG. 9B indicates a condition where the temperature of the oil isapproximately 130 degrees C. On this occasion, a straight line L1 inFIGS. 9A-9B indicates a relation between the discharge pressure of theworking oil, discharged from both of the first outlet port 31 and thesecond outlet port 32, and the rotational speed of the rotor 2. Further,a straight line L2 in FIGS. 9A-9B indicates a relation between thedischarge pressure of the working oil, discharged only from the firstoutlet port 31 and the rotational speed of the rotor 2. In FIGS. 9A-9B,hatching areas W1-W4 indicate the oil pressure required at each part tobe supplied with the working oil. More particularly, W1 indicates arequired oil pressure for the valve timing control apparatus, W2indicates a required oil pressure for a crank journal, W3 indicates arequired oil pressure for a piston jet, which supplies piston coolingoil within a high revolving-speed region of the engine, and W4 indicatesa required oil pressure for an idling of the engine. The oil pump X isrequired to supply the working oil, the oil pressure of which is equalto, or higher than, the above described required oil pressure, to thedischarge oil passage 5.

The operation of the first control valve 4 and the second control valve7 in a condition where the temperature of the working oil is in thenormal temperature region (equal to, or lower than, approximately 110degrees C.), in other words, in a condition where the temperature of theworking oil does not satisfy the temperature condition J will beexplained hereinafter. On this condition, the second control valve 7comes into a normal state in which the second control chamber 44 of thefirst control valve 4 is communicated with the feedback oil passage 6 asillustrated in FIGS. 2-6. In this normal state, the second valve body 72of the second control valve 7 is located at a position in which thefirst communicating port 71 d communicating with the first intermediateoil passage 91 is communicated with the communicating passage 71 fcommunicating with the low pressure port 71 b through the third oilpassage 72 a. Accordingly, the second valve chamber 44 of the firstcontrol valve 4 communicates with the feedback oil passage 6. Further,in a condition where the temperature of the working oil is in the normaltemperature region (equal to, or lower than, approximately 110 degreesC.), in other words, in a condition where the second control valve 7 isheld at the normal state, the first control valve 4 activates the firstvalve body 42 to achieve states of A-E and controls the dischargepressure of the working oil to be discharged to the discharge oilpassage 5. Illustrated in FIG. 9A is a relation between the rotationalspeed of the rotor 2 and the discharge pressure of the working oil fromthe discharge oil passage 5 under the above described circumstances.

State A will be explained hereinafter with reference to FIG. 2.Immediately after an engine starting, or the like, within a lowrevolving-speed region in which the rotational speed of the rotor 2 isat a lower degree (e.g., the rotational speed of the rotor is equal to,or less than, 1,500 rotation), and within a predetermined first region Idesignated at the lowest pressure region as illustrated in FIG. 9A, in acondition where the discharge pressure of the working oil from both ofthe first outlet port 31 and the second outlet port 32 is at a lowerdegree, the first valve body 42 of the first control valve 4 positionsat the last end portion of the first valve housing 41 at the first valvechamber 43 side, and the first control valve 4 performs a control forsupplying the working oil discharged from both of the first outlet port31 and the second outlet ports 32 to the discharge oil passage 5.

More particularly, the first valve body 42 closes the first and secondfeedback ports 41 c and 41 d and communicates the first oil passage 42 awith the port connecting oil passage 51 at both of the second outletport 32 side and the first outlet port 31 side. Thereby, the working oildischarged from the second outlet port 32 is supplied to the dischargeoil passage 5 through the first control valve 4 and the first outletport 31. In other words, in a condition where the oil pressure of theworking oil (the discharge pressure) in the discharge oil passage 5 isin the predetermined first region I, the first control valve 4communicates both of the first and second outlet ports 31 and 32 withthe discharge oil passage 5, and performs a control for supplying theworking oil discharged from both of the first and second outlet ports 31and 32 to the discharge oil passage 5. On this occasion, an amount ofthe working oil to be supplied to the discharge oil passage 5 becomes asum of a discharge amount of the first outlet port 31 and that of thesecond outlet port 32. Further, on this occasion, the oil pressure ofthe working oil (the discharge pressure) in the discharge oil passage 5can obtain a characteristic indicated by line O-P illustrated in FIG.9A. More particularly, the oil pressure of the working oil (thedischarge pressure) in the discharge oil passage 5 can obtain acharacteristic that the discharge pressure increases in response to theincrease of the rotational speed of the rotor 2.

The biasing force of the spring 45 a of the biasing mechanism 45 andconditions such as a position, a shape, or the like, of the first oilpassage 42 a and the second oil passage 42 b are appropriatelydesignated to achieve the states of A-E by activating the first valvebody 42 on the basis of degree of the oil pressure of the working oil(the discharge pressure) in the discharge oil passage 5.

State B will be explained hereinafter with reference to FIG. 3. In acondition where the discharge pressure of the working oil from both ofthe first and second outlet ports 31 and 32 is increased in accordancewith the increase of the rotational speed of the rotor 2, and in acondition where the discharge pressure of the working oil exceeds thefirst region I and reaches a second region I designated at a higherpressure side than the first region I, the first control valve 4performs a control for supplying some of the working oil from both ofthe first and second outlet ports 31 and 32 to the discharge oil passage5 and performs a control for supplying some of the working oil to thefeedback oil passage 6 from the first feedback port 41 c as illustratedin FIG. 3.

More particularly, the first valve body 42 moves to the second valvechamber 44 side (an upper side as viewed in FIG. 2) to some degree fromthe last end portion of the first valve housing 41 at the first valvechamber 43 side as illustrated in FIG. 2 and communicates the first oilpassage 42 a of the first valve body 42 with the port connecting oilpassage 51, at both of the second outlet port 32 side and the firstoutlet port 31 side, and with the feedback oil passage 6 while closingthe second feedback port 41 d. Thereby, some of the working oildischarged from the second outlet port 32 is supplied to the dischargeoil passage S through the first control valve 4 and the first outletport 31, and some of the working oil is supplied to the feedback oilpassage 6. In other words, in a condition where the oil pressure of theworking oil (the discharge pressure) in the discharge oil passage 5 isin the second region II, the first control valve 4 communicates both ofthe first and second outlet ports 31 and 32 with both of the dischargeoil passage 5 and the feedback oil passage 6, and supplies some of theworking oil discharged from both of the first and second outlet ports 31and 32 to the discharge oil passage 5 and some of the working oil to thefeedback oil passage 6. On this occasion, the oil pressure of theworking oil (the discharge pressure) in the discharge oil passage 5 canobtain a characteristic indicated by line P-Q illustrated in FIG. 9A.More particularly, on this occasion, the increase of the oil pressure ofthe working oil (the discharge oil) in the discharge oil passage 5 inresponse to the increase of the rotational speed of the rotor 2 islowered because a communication path to the feedback oil passage 6 isestablished.

State C will be explained hereinafter with reference to FIG. 4. In acondition where the discharge pressure of the working oil from both ofthe first and second outlet ports 31 and 32, the first and second outletports 31 and 32 being in a condition where some of the working oil issupplied to the feedback oil passage 6, exceeds the second region II andreaches a third region III designated at a higher pressure side than thesecond region II in accordance with the increase of the rotational speedof the rotor 2, the first control valve 4 performs a control forsupplying the working oil discharged from the first outlet port 31 tothe discharge oil passage 5 and performs a control for supplying theworking oil discharged from the second outlet port 32 to the feedbackoil passage 6.

More particularly, the first valve body 42 moves to the second valvechamber 44 side (an upper side as viewed in FIG. 3) to some degree froma position illustrated in FIG. 3 and communicates the first oil passage42 a with the port connecting oil passage 51 at the second outlet port32 side, and the feedback oil passage 6 through the first feedback port41 c while closing the second feedback port 41 d. On this occasion, thesecond oil passage 42 b communicates only with the port connecting oilpassage 51 at the first outlet port 31 side. Thereby, the working oildischarged from the second outlet port 32 is supplied to the feedbackoil passage 6 and the working oil discharged from the first outlet port31 is supplied to the discharge oil passage 5. In other words, in acondition where the oil pressure of the working oil (the dischargepressure) in the discharge oil passage 5 is in the third region III thefirst control valve 4 interrupts a communication path between the secondoutlet port 32 and the discharge oil passage 5, establishes acommunication path between the second outlet port 32 and the feedbackoil passage 6, and further establishes a communication path between thefirst outlet port 31 and the discharge oil passage 5, and accordinglyperforms a control for supplying the working oil discharged from thefirst outlet port 31 to the discharge oil passage 5. On this occasion,the oil pressure of the working oil (the discharge pressure) in thedischarge oil passage 5 can obtain a characteristic indicated by lineQ-R illustrated in FIG. 9A. More particularly, on this occasion, anamount of the working oil to be supplied to the discharge oil passage 5becomes substantially equal to an amount of the working oil dischargedfrom the first outlet port 31.

State D will be explained hereinafter with reference to FIG. 5. In acondition where the discharge pressure of the working oil from the firstoutlet port 31 exceeds the third region III and reaches a fourth regionIV designated at a higher pressure side than the third region III inaccordance with the increase of the rotational speed of the rotor 2, thefirst control valve 4 performs a control for supplying the working oildischarged from both of the first and second outlet ports 31 and 32 tothe discharge oil passage 5 as illustrated in FIG. 5.

More particularly, the first valve body 42 moves to the second valvechamber 44 side (an upper side as viewed in FIG. 4) to some degree froma position illustrated in FIG. 4 and establish a communication pathbetween the second oil passage 42 b and the port connecting oil passage51 at both of the second outlet port 32 side and the first outlet port31 side, and interrupts a communication path between the port connectingoil passage 51 and the first feedback port 41 c, and further closes thesecond feedback port 41 d. Thereby, the working oil discharged from thesecond outlet port 32 is supplied to the discharge oil passage 5 throughthe first control valve 4 and the first outlet port 31. In other words,in a condition where the oil pressure of the working oil (the dischargepressure) in the discharge oil passage 5 is in the fourth region IV, thefirst control valve 4 establish a communication path between the both ofthe first and second outlet ports 31 and 32 and the discharge oilpassage 5, and accordingly performs a control for supplying the workingoil discharged from both of the first and second outlet ports 31 and 32to the discharge oil passage 5. On this occasion, an amount of theworking oil to be supplied to the discharge oil passage 5 becomes a sumof an amount of the discharge pressure from the first outlet port 31 andthat of the second outlet port 32. According to an example illustratedin FIG. 9A, the oil pressure of the working oil (the discharge pressure)in the discharge oil passage 5 rapidly increases as indicated by lineR-S. Then, in a condition where the oil pressure of the working oilcorresponds to the discharge pressure from both of the first and secondoutlet ports 31 and 32, and in a condition where the discharge pressureof the working oil corresponds to line S-T illustrated in FIG. 9A, thedischarge pressure of the working oil reaches the fifth region V andthus the discharge pressure is relieved.

State E will be explained hereinafter with reference to FIG. 6. In acondition where the discharge pressure of the working oil from both ofthe first and second outlet ports 31 and 32 is increased, the pressureof the working oil exceeds the fourth region IV and reached the fifthregion V designated at a higher pressure side than the fourth region IV.On this occasion, the first control valve 4 performs a control forsupplying some of the working oil discharged from both of the first andsecond outlet ports 31 and 32 to the discharge oil passage 5 asillustrated in FIG. 6, and performs a control for supplying some of theworking oil to the feedback oil passage 6 through the first feedbackport 41 c. Further, the first control valve 4 supplies some of theworking oil to the feedback oil passage 6 by establishing acommunication path between the first valve chamber 43 and the secondfeedback port 41 d.

More particularly, the first valve body 42 moves to the second valvechamber 44 side (an upper side as viewed in FIG. 5) to some degree froma position illustrated in FIG. 4 and communicates the second oil passage42 b of the first valve body 42 with the port connecting oil passage 51at both of the second outlet port 32 side and the first outlet port 31side and the feedback oil passage 6. Further a communication pathbetween the first valve chamber 43 and the second feedback port 41 d isestablished. Thereby, some of the working oil discharged from the secondoutlet port 32 is supplied to the discharge oil passage 5 through thefirst control valve 4 and the first outlet port 31 and some of theworking oil is supplied to the feedback oil passage 6. Further, some ofthe working oil supplied to the discharge oil passage 5 is supplied tothe feedback oil passage 6 through the first transmission oil passage 52and the first valve chamber 43. In other words, in a condition where theoil pressure of the working oil (the discharge pressure) in thedischarge oil passage 5 is in the fifth region V, the first controlvalve 4 communicates both of the first and second outlet ports 31 and 32with the discharge oil passage 5 and the feedback oil passage 6, andaccordingly performs a control for supplying some of the working oildischarged from both of the first and second outlet ports 31 and 32 tothe discharge oil passage 5 and performs a control for supplying some ofthe working oil to the feedback oil passage 6. On this occasion, the oilpressure of the working oil (the discharge pressure) in the dischargeoil passage 5 can obtain a characteristic indicated by line S-Tillustrated in FIG. 9A. More particularly, on this occasion, theincrease of the oil pressure of the working oil (the discharge pressure)in the discharge oil passage 5 in response to the increase of therotational speed of the rotor 2 is lowered because the communicationpath to the feedback oil passage 6 is established.

By means of the operation of the first control valve 4, the required oilpressure for the valve timing control apparatus (area W1 in FIG. 9A) canbe ensured by rapidly increasing the oil pressure (line O-P in FIG. 9A)in a condition where the rotational speed of the rotor 2 is at a lowerdegree (a low revolving-speed region of the engine). Further, by meansof the operation of the first control valve 4, a load applied to theengine can be reduced by lowering an operation resistance of the oilpump X by controlling the oil pressure at a lower degree (lines P-Q andQ-R in FIG. 9A) for ensuring the required oil pressure for the crankjournal (area W2 in FIG. 9A) in a condition where the rotational speedof the rotor 2 is at a medium degree (a medium revolving-speed region ofthe engine). Moreover, by means of the operation of the first controlvalve 4, the oil pressure of higher degree (lines R-S and S-T in FIG.9A) can be generated for ensuring the required oil pressure for thepiston jet (area W3 in FIG. 9A) in a condition where the rotationalspeed of the rotor 2 is at a higher degree (the high revolving-speedregion of the engine)

The operation of the first control valve 4 and the second control valve7 in a condition where the temperature of the working oil exceedsapproximately 110 degrees C. will be explained hereinafter. On thisoccasion, the second control valve 7 comes into the high temperaturestate in which the second chamber 44 is communicated with the dischargeoil passage 5 as illustrated in FIG. 8 after passing through a mediumstate in which the second valve chamber 44 is communicated with both ofthe discharge oil passage 5 and the feedback oil passage 6 asillustrated in FIG. 7. Then the first control valve 4 establishes acommunication path between the second valve chamber 44 and the firstvalve chamber 43 to conform the oil pressure thereof and moves the firstvalve body 42 to the last end portion of the first valve housing 41 atthe first valve chamber 43 side by means of the biasing mechanism 45.Thereby, the first control valve 4 is held at the state A regardless ofconditions of the oil pressure of the working oil (the dischargepressure) in the discharge oil passage 5, and performs a control forsupplying the working oil discharged from both of the first and secondoutlet ports 31 and 32 to the discharge oil passage 5.

The medium state is explained hereinafter with reference to FIG. 7. In acondition where the temperature of the working oil becomes approximately110 degrees C., the heat-sensitive expanding and contracting member 73 aof the second valve body 72 starts to expand in the direction of thereciprocation of the second valve body 72, and thereby the elasticmember 73 b provided at an opposed position from the second valve body72 is compressed and the second valve body 72 moves downwards asillustrated in FIG. 7. Thereby, the third oil passage 72 a iscommunicated with the high pressure port 71 a, the low pressure port 71b, the first communicating port 71 d and the second communicating port71 e. Accordingly, the second chamber 44 of the first control valve 4communicates with both of the discharge oil passage 5 and the feedbackoil passage 6, and the working oil is began to flow into the secondvalve chamber 44. The second control valve 7 temporarily comes into themedium state on the way of shifting to the high temperature state. Thesecond control valve 7 comes into the high temperature state by furtherexpanding of the heat-sensitive expanding and contracting member 73 a.

The high temperature state is explained hereinafter with reference toFIG. 8. In a condition where the temperature of the working oil becomesequal to, or higher than, approximately 110 degrees C., that is, in acondition where the temperature of the working oil satisfies thetemperature condition J, the second control valve 7 comes into the hightemperature state. On this occasion, the heat-sensitive expanding andcontracting member 73 a of the valve body operating mechanism 73 furtherexpands in the direction of the reciprocation of the second valve body72, and thereby the elastic member 73 b is further compressed, and thesecond valve body 72 moves downwards as illustrated in FIG. 8.Therefore, the third oil passage 72 a is communicated with the highpressure port 71 a and the second communicating port 71 e. Accordingly,the second chamber 44 of the first control valve 4 communicates with thedischarge oil passage 5 through the second transmission oil passage 53.Therefore, the second valve chamber 44 of the first control valve 4communicates with the first valve chamber 43 through the discharge oilpassage 5, and the oil pressure in the second valve chamber 44 and thatof the first valve chamber 43 becomes approximately equal. On thisoccasion, the first control valve 4 performs a control for moving thefirst valve body 42 to the last end portion of the first valve housing41 at the first valve chamber 43 side by means of the biasing mechanism45. Thereby, the first control valve 4 is held at the state A regardlessof the conditions of the oil pressure of the working oil (the dischargepressure) in the discharge oil passage 5, and performs a control forsupplying the working oil discharged from both of the first and secondoutlet ports 31 and 32 to the discharge oil passage 5.

On this occasion, regardless of the condition of the oil pressure of theworking oil (the discharge pressure) in the discharge oil passage 5corresponding to any one of the regions I-IV, the oil pressure of theworking oil (the discharge pressure) in the discharge oil passage 5 canobtain a characteristic indicated by line O-S illustrated in FIG. 9B.More particularly, on this occasion, the discharge pressure is increasedin response to the increase of the rotational speed of the rotor 2.According to the embodiment of the present invention, in order toprevent the oil pump X from being damaged, some of the working oil inthe discharge oil passage 5 is supplied to the feedback oil passage 6for relieving the discharge pressure by means of a relief valve (notshown) provided at the discharge oil passage 5 in a condition where theoil pressure of the working oil (the discharge pressure) in thedischarge oil passage 5 corresponds to the fifth region V designated atthe higher pressure side than the fourth region IV. On this occasion,the oil pressure of the working oil (the discharge pressure) in thedischarge oil passage 5 can obtain a characteristic indicated by lineS-T illustrated in FIG. 9B. More particularly, on this occasion, theincrease of the oil pressure of the working oil (the discharge pressure)in the discharge oil passage 5 in response to the increase of therotational speed of the rotor 2 is lowered.

The second control valve 7 is activated at a high temperature conditionof the oil and the first control valve 4 performs a control forsupplying the working oil discharged from both of the first and secondoutlet ports 31 and 32 to the discharge oil passage 5 regardless of theconditions of the oil pressure of the working oil (the dischargepressure) in the discharge oil passage 5. Thereby, the oil pump Xaccording to the embodiment of the present invention can ensure therequired discharge pressure at the high temperature condition of the oiland can also achieve an optimal discharge pressure within the normaltemperature region, which is a temperature region of the working oilunder the normal use conditions, in other words, less than, or equal to,approximately 110 degrees C. Accordingly, the operation resistance ofthe oil pump X can be reduced. Therefore, in a condition where the oilpump X is activated by means of the engine of the vehicle, a fueleconomy of the engine can be improved.

Illustrated in FIGS. 10A-10B are a relation, within the normaltemperature region of the working oil (approximately from roomtemperature to 110 degrees C.) and within the high temperature region ofthe working oil (approximately from 110 to 130 degrees C.), between therotational speed of the rotor 2 and the discharge pressure of theworking oil of an oil pump, which has a first control valve similar tothat of the first embodiment of the present invention and does not havea second control valve. Illustrated in FIG. 10A is a condition where thetemperature of the oil is approximately 80 degrees C., and illustratedin FIG. 10B is a condition where the temperature of the oil isapproximately 130 degrees C. A straight line L1 in FIGS. 10A-10Bindicates a relation between the discharge pressure of the working oil,discharged from both of the first outlet port 31 and the second outletport 32, and the rotational speed of the rotor 2. Further a straightline L2 in FIGS. 10A-10B indicates a relation between the dischargepressure of the working oil, discharged only from the first outlet port31, and the rotational speed of the rotor 2. A slope of the lines L1 andL2 tends to become gentle in accordance with the increase of thetemperature of the oil. It is because a degree of viscosity of theworking oil is lowered in response to the increase of the temperature ofthe oil, a degree of leak of the working oil in the parts to be suppliedwith the working oil is increased, and accordingly a rate of theincrease of the discharge pressure of the working oil relative to theincrease of the rotational speed of the rotor is lowered.

Further, as well as the oil pump X according to the first embodiment ofthe present invention, the oil pump illustrated in FIG. 10 reduces theload applied to the engine by lowering the operation resistance of theoil pump by controlling the oil pressure at the lower degree in a regionin which the rotational speed of the rotor is at the medium degree (themedium revolving-speed region of the engine), that is, in regionsindicated by line P-Q, Q-R, and R-S in FIGS. 10A-10B.

On this occasion, in a condition where the temperature of the workingoil becomes at the higher degree, the rate of the increase of thedischarge pressure of the working oil relative to the increase of therotational speed of the rotor is lowered. Therefore, in a conditionwhere the temperature of the working oil becomes at the higher degree,the rotational speed of the rotor is increased for ensuring thedischarge pressure more than, or equal to, the predetermined requiredpressure (areas W1-W4) for the parts to be supplied with the workingoil. Thus, the oil pump, which does not have the second control valve 7is configured to have a control valve, which is a valve corresponding tothe first control valve according to the first embodiment of the presentinvention, for controlling the discharge amount or the dischargepressure of the working oil relative to the rotational speed of therotor in order to ensure the discharge pressure more than, or equal to,the predetermined required pressure (areas W1-W4) for the parts to besupplied with the working oil even at an assumed highest temperature ofthe working oil as illustrated in FIG. 10B. More particularly, the pumpmain body, the control valve, or the like, of the oil pump illustratedin FIG. 10B is configured to supply the working oil, discharge pressureof which is more than, or equal to, each predetermined required oilpressure such as the required oil pressure for the valve timing controlapparatus (area W1), the required oil pressure for the crank journal(area W2), the required oil pressure for the piston jet (area W3), andthe required oil pressure for the idling of the engine (area W4), to thedischarge oil passage 5 in the whole region of the rotational speed ofthe rotor in a condition where the working oil is at approximately 130degrees C.

In a condition where the pump main body, control valve, or the like, ofthe oil pump is configured on the basis of the assumed highesttemperature, if the temperature of the working oil is within the normaltemperature region, an effect of decreasing of the operation resistanceof the oil pump may occasionally be lowered because a region, in whichthe discharge pressure of the working oil can be reduced by means of thefirst control valve 4 at the time of a medium revolving-speed region ofthe rotor, is narrowed as illustrated in FIG. 10A. More particularly, ina condition where the temperature of the working oil is at the lowerdegree, the rate of the increase of the discharge pressure of theworking oil relative to the increase of the rotational speed of therotor becomes higher. Therefore, the region in which the dischargepressure is reduced by means of the first control valve 4 is located ata lower rotational speed side as illustrated in FIG. 10A relative to acondition where the temperature of the working oil is at the higherdegree as illustrated in FIG. 10B. More particularly, the discharge oilpressure is increased in a condition where the rotational speed of therotor is relatively lower degree than the rotational speed of the rotorthat requires the required oil pressure for the piston jet (area W3).Thus, a region Y, in which a surplus discharge pressure is generated, isoccurred and an effect of decreasing of the load applied to the engineis lowered. Further, the working oil of the vehicle in practice comesinto the high temperature region (approximately from 110 to 130 degreesC.) on rare condition such as a condition where the engine is activatedfor long periods of time with a heavy load, and the working oil of thevehicle in practice is within the normal temperature region(approximately from room temperature to 110 degrees C.) under the normaluse conditions. Accordingly, with a discharge control of the working oilas illustrated in FIG. 10, the effect of decreasing of the load appliedto the engine may occasionally be low.

In contrast, with the configuration of the oil pump according to thefirst embodiment of the present invention, the second control valve 7 isactivated at the high temperature condition of the oil and the firstcontrol valve 4 performs a control for supplying the working oildischarged from both of the first and second outlet ports 31 and 32 tothe discharge oil passage 5 regardless of the conditions of the oilpressure of the working oil (the discharge pressure) in the dischargeoil passage 5. Thereby the oil pump X according to the first embodimentof the present invention can ensure the required discharge pressure atthe high temperature condition of the oil and can also achieve theoptimal discharge pressure within the normal temperature region, whichis the temperature region of the working oil under the normal useconditions, in other words, less than, or equal to, approximately 110degrees C. Therefore, as illustrated in FIG. 9A, the pump main body 1,the first control valve 4, or the like, of the oil pump X can beconfigured to widely ensure the region in which the discharge pressureof the working oil can be reduced within the normal temperature region.Accordingly, a rotational speed region of the rotor 2, in which theoperation resistance of the oil pump X can be reduced within the normaltemperature region, can be expanded and the effect of decreasing of theload applied to the engine can be improved.

With the configuration of the oil pump X having a characteristic of theabove described discharge pressure, the pump main body 1 and the firstand second outlet ports 31 and 32 may be configured that the dischargepressure of the working oil from the first outlet port 31 (the dischargepressure indicated by line Q-R in FIG. 9A) within the third region IIIin a condition where the temperature of the working oil is at a lowerlimit (approximately 110 degrees C.) of the temperature condition J(approximately from room temperature to 110 degrees C.) becomes morethan, or equal to, the required oil pressure (areas W1-W2) at the partsto be supplied with the working oil, and the discharge oil pressure ofthe working oil from the first and second oil ports 31 and 32 within thewhole regions of the rotational speed I-V (at least within the firstregion I and the fifth region V) in a condition where the temperature ofthe working oil is at a higher limit (approximately 130 degrees C.) ofthe temperature condition J becomes more than, or equal to, the requiredoil pressure (areas W1-W4) at the parts to be supplied with the workingoil. With the above described configuration, the discharge pressure,which is more than, or equal to, the required oil pressure at the partsto be supplied with the working oil, can be ensured in both conditionswhere the temperature of the working oil is at the lower limit of thetemperature condition J (approximately 110 degrees C.), at which thedischarge pressure of the working oil becomes at the lowest level whenthe temperature of the working oil does not satisfy the temperaturecondition J, and where the temperature of the working oil is at thehigher limit of the temperature condition J (approximately 130 degreesC.), at which the discharge pressure becomes at the lowest level whenthe working oil satisfies the temperature condition J. In consequence,the discharge pressure, which is more than, or equal to, the requiredoil pressure at the parts to be supplied with the working oil, can beensured under any temperature conditions.

A second embodiment of the present invention will be explainedhereinafter with reference to FIG. 11. As illustrated in FIG. 11, theconfiguration of an oil pump XII according to the second embodiment ofthe present invention is basically similar to that of the oil pump Xaccording to the first embodiment of the present invention in astructure. The same structure as described in the aforementionedembodiment is not repeatedly explained. A structure of a first valvebody 242 of a first control valve 204 is different from that of thefirst embodiment of the present invention. The first valve body 242 ofthe oil pump XII according to the second embodiment of the presentinvention does not include an oil passage corresponding to the secondoil passage 42 b of the first embodiment of the present invention, andonly includes an oil passage corresponding to the first oil passage 42 aof the first embodiment of the present invention. Therefore, the firstcontrol valve 204 of the oil pump XII according to the second embodimentof the present invention operates the first valve body 242 for achievinga similar condition to the conditions A-C (FIGS. 2-4) of the firstcontrol valve 4 according to the first embodiment of the presentinvention on the basis of degree of the discharge pressure of theworking oil to be discharged to the discharge oil passage 5 in acondition where the temperature of the working oil is within the normaltemperature region (equal to, or lower than, approximately 110 degreesC.), that is, in a condition where a second control valve 207 is held ata normal state. Further, in a condition where the discharge pressure ofthe working oil is increased, the oil pump XII according to the secondembodiment of the present invention establishes a communication pathbetween a first valve chamber 243 and a second feedback port 241 d, andsupplies some of the working oil in a discharge oil passage 205 to afeedback oil passage 206 for relieving the discharge pressure. Then, thesecond control valve 207 performs an operation similar to that of theoil pump X according to the first embodiment of the present invention.

Illustrated in FIGS. 12A-12B are a relation, within the normaltemperature region of the working oil (approximately from roomtemperature to 110 degrees C.) and within the high temperature region ofthe working oil (approximately from 110 to 130 degrees C.), between arotational speed of a rotor 202 and the discharge pressure of theworking oil in the discharge oil passage 205. FIG. 12A indicates acondition where the temperature of the oil is approximately 80 degreesC. and FIG. 12B indicates a condition where the temperature of the oilis approximately 130 degrees C. FIG. 12 according to the secondembodiment of the present invention corresponds to FIG. 9 according tothe first embodiment of the present invention.

As illustrated in FIG. 12, the oil pump XII according to the secondembodiment of the present invention, in a condition where thetemperature of the working oil is within the normal temperature region(equal to, or lower than approximately 110 degrees C.), by activatingthe first control valve 204 on the basis of degree of the dischargepressure of the working oil to be discharged to the discharge oilpassage 205, the oil pressure is rapidly increased (line O-P in FIG.12A) in a condition where the rotational speed of the rotor 202 is at alower degree (the low revolving-speed region of the engine) for ensuringthe required oil pressure for the valve timing control apparatus (areaW1 in FIG. 12A), and controls the oil pressure at the lower degree (lineP-Q and line Q-R in FIG. 12A) for ensuring the required oil pressure forthe crank journal (area W2 in FIG. 12A) in a condition where therotational speed of the rotor 202 is higher than the medium degree (themedium and high revolving-speed region of the engine). Accordingly, theload applied to the engine can be reduced by lowering the operationresistance of the oil pump XII. The oil pump performing a controlillustrated in FIG. 12A may be used as an oil pump for supplying theworking oil to an engine, which does not perform the piston jet at thehigh revolving-speed region, that is, an engine, which does not have therequired pressure for the piston jet (area W3) according to the firstembodiment of the present invention.

As well as the oil pump X according to the first embodiment of thepresent invention, the second control valve 207 is activated at the hightemperature condition of the oil and the first control valve 204performs a control for supplying the working oil discharged from both ofthe first and second outlet ports 31 and 32 to the discharge oil passage5 regardless of the conditions of the oil pressure of the working oil(the discharge pressure) in the discharge oil passage 5. Thereby the oilpump XII according to the second embodiment of the present invention canensure the required discharge pressure at the high temperature conditionof the oil and can also achieve an optimal discharge pressure within thenormal temperature region, which is the temperature region of theworking oil under the normal use conditions, in other words, less than,or equal to, approximately 110 degrees C. Accordingly, the operationresistance of the oil pump XII can be reduced. Therefore, in a conditionwhere the oil pump X is activated by means of the engine of the vehicle,a fuel economy of the engine can be improved.

Illustrated in FIGS. 13A-13B are a relation, within the normaltemperature region of the working oil (approximately from roomtemperature to 110 degrees C.) and within the high temperature region ofthe working oil (approximately from 110 to 130 degrees C.), between therotational speed of the rotor and the discharge pressure of the workingoil of an oil pump, which has a first control valve similar to that ofthe second embodiment of the present invention and does not have asecond control valve. Illustrated in FIG. 13A is a condition where thetemperature of the oil is approximately 80 degrees C., and illustratedin FIG. 13B is a condition where the temperature of the oil isapproximately 130 degrees C. FIG. 13 corresponds to FIG. 10 according tothe first embodiment of the present invention.

Further, as well as the oil pump XII according to the second embodimentof the present invention, the oil pump illustrated in FIG. 13 isprovided with a control valve (a valve corresponding to the first valveaccording to the second embodiments of the present invention) forcontrolling the discharge amount and the discharge pressure of theworking oil in order to ensure the discharge pressure more than, orequal to, the predetermined required pressure (areas W1, W2, and W4) atthe parts to be supplied with the working oil even at the assumedhighest temperature of the working oil as illustrated in FIG. 13B.

In a condition where the pump main body, control valve, or the like, ofthe oil pump is configured on the basis of the assumed highesttemperature, if the temperature of the working oil is within the normaltemperature region, the effect of decreasing of the operation resistanceof the oil pump may occasionally be lowered because the region, in whichthe discharge pressure of the working oil can be reduced by means of thefirst control valve in a condition where the rotational speed of therotor is higher than the medium degree, is narrowed as illustrated inFIG. 13A. More particularly, in a condition where the temperature of theworking oil is at the lower degree, the rate of the increase of thedischarge pressure of the working oil relative to the increase of therotational speed of the rotor becomes higher degree. Therefore, theregion in which the discharge pressure is reduced by means of the firstcontrol valve is located at a lower rotational speed side as illustratedin FIG. 13A relative to a condition where the temperature of the workingoil is at the higher degree as illustrated in FIG. 13B. Accordingly, thehigher degree of the discharge pressure of the working oil is generallyoutputted from the lower revolving-speed region of the rotor, and theregion Y, in which the surplus discharge pressure is generated, isoccurred. In consequence, the effect of decreasing of the load appliedto the engine may occasionally be lowered.

In contrast, with the configuration of the oil pump X according to thesecond embodiment of the present invention, the second control valve 207is activated at the high temperature condition of the oil and the firstcontrol valve 204 performs a control for supplying the working oildischarged from both of the first and second outlet ports 231 and 232 tothe discharge oil passage 205 regardless of the conditions of the oilpressure of the working oil (the discharge pressure) in the dischargeoil passage 205. Thereby, the oil pump XII according to the secondembodiment of the present invention can ensure the required dischargepressure at the high temperature condition of the oil and can alsoachieve the optimal discharge pressure within the normal temperatureregion, which is the temperature region of the working oil under thenormal use conditions, in other words, less than, or equal to,approximately 110 degrees C. Therefore, as illustrated in FIG. 12A, thepump main body 201, the first control valve 204, or the like, of the oilpump XII can be configured to widely ensure the region in which thedischarge pressure of the working oil can be reduced within the normaltemperature region. Accordingly, a rotational speed region of the rotor202, in which the operation resistance of the oil pump XII can bereduced within the normal temperature region, can be expanded and theeffect of decreasing of the load applied to the engine can be improved.

With the configuration of the oil pump XII having a characteristic ofthe above described discharge pressure, the pump main body 201 and thefirst and second outlet ports 231 and 232 may be configured that thedischarge pressure of the working oil from the first outlet port 231(the discharge pressure indicated by line Q-R in FIG. 12A) within thethird region III in a condition where the temperature of the working oilis at the lower limit (approximately 110 degrees C.) of the temperaturecondition J (approximately from room temperature to 110 degrees C.)becomes more than, or equal to, the required oil pressure (areas W1-W2)at the parts to be supplied with the working oil, and the discharge oilpressure of the working oil from the first and second oil ports 231 and232 in a condition where the temperature of the working oil is at thehigher limit (approximately 130 degrees C.) of the temperature conditionJ becomes more than, or equal to, the required oil pressure (areas W1,W2 and W4) at the parts to be supplied with the working oil within theregions from the first region I to the fourth region IV (at least withinthe first region I). With the above described configuration, thedischarge pressure, which is more than, or equal to, the required oilpressure at the parts to be supplied with the working oil, can beensured in both conditions where the temperature of the working oil isat the lower limit of the temperature condition J (approximately 110degrees C.), at which the discharge pressure of the working oil becomesat the lowest level when the temperature of the working oil does notsatisfy the temperature condition J, and where the temperature of theworking oil is at the higher limit of the temperature condition J(approximately 130 degrees C.), at which the discharge pressure becomesat the lowest level when the working oil satisfies the temperaturecondition J. In consequence, the discharge pressure, which is more than,or equal to, the required oil pressure at the parts to be supplied withthe working oil, can be ensured under any temperature conditions.

A third embodiment of the present invention will be explainedhereinafter with reference to FIG. 14. The same structure as describedin the aforementioned embodiments is not repeatedly explained. Asillustrated in FIG. 14, with the configuration of the oil pump XIIIaccording to the third embodiment of the present invention, the workingoil is discharged only from an outlet port 331. Therefore, a firstcontrol valve 304 according to the third embodiment of the presentinvention functions only as the relief valve for a condition where thedischarge pressure of the working oil in a discharge oil passage 305 isat the higher degree. Therefore, the first control valve 304 of the oilpump XII according to the third embodiment of the present invention isactivated on the basis of degree of the discharge pressure of theworking oil to be discharged to the discharge oil passage 305 in acondition where the temperature of the working oil is within the normaltemperature region (equal to, or lower than, approximately 110 degreesC.), that is, in a condition where the second control valve 307 is heldat the normal state. Further, in a condition where the dischargepressure of the working oil is increased, the oil pump XIII according tothe third embodiment of the present invention establishes acommunication path between a first valve chamber 343 and a secondfeedback port 341 d, and supplies some of the working oil in thedischarge oil passage 305 to a feedback oil passage 306 for relievingthe discharge pressure.

The oil pump XIII according to the third embodiment of the presentinvention can perform a control not to operate the first control valve304 serving as the relief valve in a condition where the temperature ofthe working oil is at the higher degree. Accordingly, the oil pump XIIIaccording to the third embodiment of the present invention can ensurethe required discharge pressure at the high temperature condition of theoil and can also achieve the optimal discharge pressure within thenormal temperature region, which is the temperature region of theworking oil under the normal use conditions, in other words, less than,or equal to, approximately 110 degrees C.

According to the embodiments of the present invention, theheat-sensitive expanding and contracting member 73 a, 273 a, 373 a ofthe second control valve 7, 207, 307 includes a spring made of shapememory alloy. However, the invention is not limited thereto.Alternatively or in addition, a thermostat wax, a bimetal, or the likecan be used for the heat-sensitive expanding and contracting member 73a, 273 a, 373 a. Further, alternatively or in addition, combination ofthe shape memory alloy, thermostat wax, and the bimetal may be used forthe heat-sensitive expanding and contracting member 73 a, 273 a, 373 a.

According to the embodiments of the present invention, the secondcontrol valve 7, 207, 307 establishes the communication path between thesecond valve chamber 44, 244, 344 and the first valve chamber 43, 243,343 in a condition where the temperature of the working oil satisfiesthe predetermined temperature condition J. However, the invention is notlimited thereto. Alternatively, or in addition, the second control valve7, 207, 307 may be configured to adjust an amount of the working oil tobe flowed into the second valve chamber 44, 244, 344 of the firstcontrol valve 4, 204, 304. Thereby, the second control valve 7, 207, 307may control the oil pressure of the working oil to be flowed into thesecond valve chamber 44, 244, 344 by adjusting the amount of the workingoil to be flowed into the second valve chamber 44, 244, 344. With such aconfiguration, the oil pump can be configured without the biasingmechanism 45, 245, 345, or the like, for biasing the first valve body42, 242, 342 of the first control valve 4, 204, 304 toward the firstvalve chamber 43, 243, 343 side. The oil pump without the biasingmechanism 45, 245, 345 controls the position of the first valve body 42,242, 342 in the housing 41, 241, 341 by means of the balance between theoil pressure of the working oil flowed into the second valve chamber 44,244, 344 and the discharge pressure of the working oil applied to thefirst valve chamber 43, 243, 343.

According to the embodiments of the present invention, the oil pumpapplied to the vehicle engine is explained. However, the invention isnot limited thereto. Alternatively, or in addition, the presentinvention can be applied to any oil pump other than the oil pump of thevehicle or the engine.

According to the embodiment of the present invention, the second controlvalve can adjust the position of the valve body on the basis of degreeof the temperature of the working oil by controlling the oil pressure ofthe working oil to be flowed into the second valve chamber facing thefirst valve chamber to which the discharge pressure of the working oilis applied. The second valve chamber is provided to face the first valvechamber across the valve body. The oil pump according to the embodimentsof the present invention can activate the first control valve, whichcontrols the discharge pressure of the working oil, without providing aproportional electromagnetic control mechanism such as a solenoid, orthe like. Further, because the second control valve is providedindependently from the first control valve to which the dischargepressure from the pump main body is applied, the second control valve,which is activated on the basis of degree of the temperature of theworking oil, is not influenced by the pulsation of the dischargepressure of the working oil. Accordingly, the second control valve canbe made of a low fatigue strength material.

The present invention is applicable as long as the first control valveincludes the biasing mechanism biasing the first valve body in thedirection in which the first valve body is moved toward the first valvechamber, and the second control valve establishing the communicationpath between the second valve chamber and the first valve chamber in acondition where the temperature of the working oil satisfies thepredetermined temperature condition.

With the configuration of the oil pump according to the embodiments ofthe present invention, in a condition where the temperature of theworking oil satisfies the predetermined temperature condition, thecommunication path between the second valve chamber and the first valvechamber is established and the oil pressure in the second valve chamberand that of the first valve chamber becomes approximately equal. Then,the first valve body of the first control valve moves to the last endportion of the first valve housing at the first valve chamber side bymeans of the biasing mechanism. Accordingly, because the first controlvalve is configured to control the optimal discharge pressurecorresponding to the temperature of the working oil in a condition wherethe first valve body is positioned at the last end portion of the firstvalve housing at the first valve chamber side, the oil pump canappropriately control the discharge pressure on the basis of degree ofthe temperature of the working oil with a simple structure.

The present invention is applicable as long as the second control valveincludes the second valve body reciprocating in the second valve housingand switching the control whether to establish or interrupt thecommunication path between the second valve chamber and the first valvechamber of the first control valve, and the valve body operatingmechanism activating the second valve body by means of theheat-sensitive expanding and contracting member, which is expanded andcontracted in the direction of the reciprocation of the second valvebody on the basis of degree of the temperature of the working oil.

According to the embodiments of the present invention, the temperatureof the working oil is transmitted, and the second valve body isactivated by means of the heat-sensitive expanding and contractingmember, which is expanded and contracted in the direction of thereciprocation of the second valve body on the basis of degree of thetemperature of the working oil. Therefore, the oil pump canappropriately control the discharge pressure corresponding to thetemperature of the working oil with the simple structure. Further,because the second control valve is provided independently from thefirst control valve to which the discharge pressure from the pump mainbody is applied, the heat-sensitive expanding and contracting member ofthe second control valve is not influenced by the pulsation of thedischarge pressure of the working oil. Accordingly, the second controlvalve can be made of the low fatigue strength material.

The principles, preferred embodiments and mode of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims, be embracedthereby.

1. An oil pump comprising: a first control valve including: a firstvalve body provided in a first valve housing for reciprocating therein,the first valve body for controlling discharge pressure of working oildischarged from a pump main body on the basis of a position of the firstvalve body in the first valve housing; a first valve chamber formed inthe first valve housing at a first side of the first valve body, thefirst valve chamber being applied with the discharge pressure of theworking oil from the pump main body; and a second valve chamber formedin the first valve housing at a second side of the first valve body, thesecond valve chamber being supplied with the working oil; and a secondcontrol valve activated on the basis of degree of the temperature of theworking oil, the second control valve for controlling oil pressure ofthe working oil flowed into the second valve chamber.
 2. The oil pumpaccording to claim 1, wherein the first control valve includes a biasingmechanism biasing the first valve body in a direction in which the firstvalve body is moved toward the first valve chamber, and the secondcontrol valve establishes the communication path between the secondvalve chamber and the first valve chamber in a condition where thetemperature of the working oil satisfies a predetermined temperaturecondition.
 3. The oil pump according to claim 1, wherein the secondcontrol valve includes a second valve body reciprocating in a secondvalve housing and switching a control whether to establish or interruptthe communication path between the second valve chamber and the firstvalve chamber, and a valve body operating mechanism operating the secondvalve body by means of a heat-sensitive expanding and contractingmember, which is expanded and contracted in a direction of areciprocation of the second valve body on the basis of degree of thetemperature of the working oil.
 4. The oil pump according to claim 1,wherein the valve body operating mechanism includes the heat-sensitiveexpanding and contracting member provided at a first side of the secondvalve body and an elastic member provided at a second side of the secondvalve body.
 5. The oil pump according to claim 1, wherein theheat-sensitive expanding and contracting member includes a shape memoryalloy, a thermostat wax, or a bimetal.